Space-based Gravitational-wave Observatory (SGO)- Mid

1. Space-based Gravitational-wave Observatory(SGO)-Mid MinimumCost 3-arm/6-link LISA-like Mission Presented by Jeff Livas for the SGO Core Team

2. Concept Description • Rationale for the configuration • Try to find lowest cost 6 links for LISA-like mission • Benefits of 6 links • Instantaneous/continuous polarization information • Sagnac enables noise estimation • Redundancy: tolerates loss of up to 2 links while still doing science • SGO-Mid differs from LISA by: • Arm length reduced from 5 to 1 Gm • Mission length reduced from 5 to 2 years. • Starting distance from Earth reduced by ~2.5X to a 9-degree trailing orbit. • Telescope diameter reduced from 40 to 25 cm • Laser power out of telescope reduced from 1.2 to 0.7 W (end of life). • In-field guiding instead of articulating optical assembly

3. SGO-Mid Science

4. SGO-Mid Science • Covers decadal-endorsed science • Generally detects fewer sources of all types • Main science risk is shortened mission duration • Event rates uncertain • Science return lower if event rates are lower

5. Parameter Estimation

6. SGO-Mid Configuration • Small telescope means optical bench sets height • In-field guiding simplifies optical assembly • Launch stack fits easily into a Falcoln 9 fairing • drift away orbit requires little fuel, simplifying prop module Low High Mid

7. Scientific Payload

8. Orbits/trajectory • 2 year drift-away • ~ 6 deg/year drift rate starting at 9 degrees • 2 year end of mission similar to nominal SGO-high orbital station • Communications requirements similar to SGO-high • Stable constellation • DL/L ~0.06 • Da~ 0.6 • Dv~ 2 m/s • 18 month trajectory • Optimized DV ~ 130 m/s (each)

9. Cost Estimate • Cost model includes • Non-recurring Engineering costs • “learning curve” for multiple copies • 20% additional management reserves • Scaling with mission lifetime • Scaling rates for NRE, learning curve based on • Spacecraft/Vehicle-Level Cost Model • NASA/Air Force Cost Model